1. Field of the Invention
This invention relates generally to the field of antenna structures for two-way portable transceivers. More particularly, this invention relates to low profile antenna structures suitable for packaging within the battery enclosure of a portable two-way transceiver or otherwise enclosed within the transceiver housing.
2. Background
A conventional portable two-way transceiver is depicted generally as transceiver 10 in FIG. 1.
An exemplary transceiver is the 800 Mhz MX-300 series of radios manufactured by Motorola, Inc., the Assignee of the present invention. Such transceivers normally include an external antenna 12 attached to the uppermost portion of transceiver 10. The electronic circuitry which makes up the transmitter and receiver (ie. the transceiver itself) are normally housed primarily in a housing 14. A battery pack 16 typically attaches to the bottom portion of housing 14. This battery pack normally encloses one or more electrical battery cells along with associated components and circuitry necessary to effect and control charging of the battery cells.
Transceiver 10 is shown to have an overall height of L1 made up of the height of the antenna shown as L2, the height of the housing shown as L3 and the height of the battery pack shown as L4. For a typical model of the MX-300 series transceiver, the overall height L1 is approximately 15.4 inches, L2 is approximately 7.7 inches, L3 is approximately 4.1 inches, and L4 is approximately 3.6 inches.
The present invention allows for elimination of the conventional top-mounted antenna 12 and provides for a highly efficient radiating structure which may be placed within the battery pack or receiver housing. One resulting configuration is shown in FIG. 2 generally as transceiver 20. By utilizing the present invention within the battery pack, the overall height may be significantly reduced. The resulting transceiver 20 has an overall height shown as L5 made up of the height of transceiver housing 14 which remains unchanged and the slightly increased height of the battery pack/antenna 22 shown as L6. In one embodiment of the present invention, height L6 is only 4.6 inches resulting in an overall height L5 of 8.7 inches without sacrifice of battery capacity. This is an overall reduction in height of 6.7 inches. Of course, further height reductions are possible if battery life is not a prime consideration. This height reduction is possible without unacceptable compromise of antenna performance. Similar height reductions are possible with the antenna structure integrated within the transceiver housing rather than the battery enclosure.
While the specific antenna configuration disclosed herein may be utilized in locations other than a battery enclosure a number of important advantages are attained by placing the antenna in the battery enclosure. The electrical battery cells help to provide an excellent counterpoise for operation of the antenna structure and helps shield radiation from sensitive radio components. In addition, the antenna is well protected and less likely to be damaged when enclosed within the battery pack. Also, by removing the antenna from the upper surface of transceiver housing 14, more vital space for transceiver controls is free. This aspect is becoming increasingly important as the level of complexity of two-way portable transceivers is rapidly increasing.